Extended Lists let you attach additional data to contacts in an existing Marketing List without copying contacts into multiple lists. This is useful when you need to reference extra attributes like subscription preferences, product details, geographic data, or transaction history while keeping your primary audience list as the single source of truth.
Quick Reference (Advanced Users) - Click to Expand
- Upload your additional data as an Extension List.
- Define an Extended List under a Marketing List using a shared unique key.
- The Lookup Column in the Extension List must be unique (no duplicates).
- Use a Joined Column Prefix so extended fields are easy to identify in segmentation and personalization.
- Keeping one primary list and extending it reduces confusion compared to maintaining multiple overlapping lists.
Before you begin
Extended Lists are created by matching a column in your Marketing List to a unique key column in an Extension List. For example, you might match a contact ID, account ID, or email address.
Avoid creating additional Marketing Lists just to hold extra attributes. Multiple lists with similar contacts can make it difficult to know where contacts are stored and where updates should be applied later. Extended Lists help you keep data centralized while still using additional fields.
Upload an Extension List
The first step is to bring your additional data into Act-On as an Extension List.
- Go to Lists > Other Lists > Extension Lists.
- Click New.
- Follow the wizard to upload your list.
- If you do not see Extension Lists, your account may not have this option enabled. Contact support to request access.
Define an Extended List on your Marketing List
Once your Extension List is uploaded, you can define an Extended List under a Marketing List. This adds the Extension List fields as “lookup” fields that can be used for segmentation and email personalization.
- In Lists > Marketing Lists, hover over the Marketing List you want to extend.
- Open the list dropdown menu, then select Define Extended List.
- Enter a name in Extended List Name.
- Select Add Lookup Column, then complete the lookup details (explained below).
- Click Save.
- The Extended List appears nested under the Marketing List, similar to a segment.
Lookup settings explained
When defining the Extended List, you are telling Act-On how to match records between the two lists.
- Extension List to Look Up: The Extension List that contains the additional fields you want to access.
- Marketing List Column to Extend: The column in your Marketing List that matches the lookup key in the Extension List.
- Lookup Column: The unique key column in the Extension List used for matching.
Important: This column must contain unique values (no duplicates). Act-On uses this value to match each Marketing List record to the correct Extension List record. - Joined Column Prefix: A prefix added to each Extension List column name so the extended fields are easy to identify when you use them in segmentation and email personalization.
If you need additional lookup fields (for example, multiple key options), you can repeat Add Lookup Column to add more matches.
After saving, open the Extended List to confirm the joined fields appear as expected. Extended Lists support most of the same actions as the parent Marketing List, including creating segments.
Update the Extension List
You can update Extension Lists at any time. For example, transaction or product data may change frequently. When the Extension List is updated, the connected Extended List reflects the updated information automatically.
You can update an Extension List in two ways:
- Append to this List (manual update): Open the Extension List dropdown menu and use Append to this List to upload an updated Excel or CSV file.
- FTP sync (scheduled update): Use an FTP-based import workflow to refresh the Extension List on a schedule.